The magic number, as It appears frequently in Harry Potter, is 7. Voldemort originally wanted 7 pieces of his soul - 6 horcrux and himself.
He had created 5 and was planning on using something when he killed Harry for his 6th. Obviously his plan backfired, so he thought and he never accomplished his goal. His soul did however latch onto Harry creating his 6th horcrux.
Later on, Voldemort created what he thought was his 6th and final by killing the old man who used to be his family’s Gardner and making Nagini his 7th.
This can be confusing because in the book and movie they keep mentioning 1 less then you would count up in your head, because no one is counting Harry until the very end.
There are 7 horcrux total and Voldemort himself, but he only meant to create 6. Voldemort is not a horcrux.